Hexose transport and mucosal morphology in the small intestine of the zinc-deficient rat

Abstract

1. Immature male Wistar rats were given a zinc-depleted semi-synthetic diet (2 mg Zn/kg diet) for 4 weeks.Control groups received a similar diet containing 60 mg Zn/kg diet, either ad lib. or in amounts matched to the consumption of the Zn-deficient group. Rates of growth and food conversion efficiency were markedly lower in the Zn-deficient group compared to controls.2. The phloridzin-sensitive uptake of galactose and 3-0-methyl glucose by everted jejunal rings from each group was measured over a range of concentrations. Kinetic analysis revealed that the maximum transport rate (Vmax) for the uptake of both sugars was significantly higher in the Zn-deficient group than in the control groups.3. The villi, microdissected from samples of proximal jejunum, were significantly shorter and narrower across the base in the Zn-deficient group than those of the control groups, but were present in greater numbers per unit serosal area.

Hexose absorption from jejunal loopsin situin zinc-deficient and Zn-supplemented rats

“…Such absorption studies performed at a single substrate concentration, and without reference to intestinal structural changes, do not lend themselves to investigations of absorption mechanisms at the cellular level. Our investigations, which include both kinetic and morphological studies, suggest that these mechanisms are altered in response to dietary Zn-depletion (Southon et al 1984). There also appeared to be some response to prolonged feed restriction in the control animals, in that rates of galactose transport per unit dry weight and per unit length of jejunum tended to be higher in this group of rats compared with ad lib.-fed controls.…”

“…In a previous study we investigated the phloridzin-sensitive uptake of galactose and 3-0-methyl glucose in vitro by everted jejunal rings from Zn-deficient and Zn-supplemented rats. The study demonstrated that Zn-deficiency was accompanied by a marked enhancement of carrier-mediated hexose uptake in the jejunal mucosa, which appeared to result from the presence of larger numbers of carrier sites per unit dry weight of intestine (Southon et al 1984). This increased capacity to transport substrate across the brush-border membrane however does not necessarily imply an increased rate of net trans-epithelial transport.…”

“…It has been argued that an increase in villous surface, such as observed in alloxan-induced diabetic rats, is associated with hyperphagia and consequent increased lumenal nutrition (Lorenz-Meyer et al 1977), but in this instance villous density remained unchanged. Alterations in mucosal morphology and cellular proliferation in the Zn-deficient rat are discussed in detail elsewhere (Southon et al 1984(Southon et al , 1985.…”

“…The third group was fed ad lib. The composition of the semi-synthetic diet was similar to that previously described (Southon et al 1984) with the addition of 5 g methionine/kg diet. All rats received distilled water ad lib.…”

Zinc Supplementation Attenuated Calcium-High Diet Effect on Zinc Status and Carbohydrate Metabolism of Non-Diabetic and Diabetic Rats

“…Humidity was around 40%. Standard rat diet [20] and water were available ad libitum for the duration of the experiments. The diet consisted (in grams per kg of diet) of cornstarch 326, sucrose 326, proteins 168 (egg-white solids), lipids 80 (corn oil), fibre 40 (cellulose), vitamin mix (sigma) and mineral mix 40.…”